Patent Document 1 (EP 1656498 B1), Patent Document 2 (JP 6-108948A corresponding to U.S. Pat. No. 4,826,080), and Patent Document 3 (JP Patent No. 4054621 corresponding to US 2003/0052198 A1) disclose regarding fuel injection devices provided with: a pressure chamber that exerts fuel pressure on a valve member for interrupting and allowing fuel injection from a nozzle hole; and a pressure regulating mechanism that regulates the pressure in the pressure chamber to move the valve member. With respect to the fuel injection devices, it is proposed to use a pressure-responding control member that is moved in response to a pressure change caused by opening/closing of an electromagnetic valve for the pressure regulating mechanism. Such a control member receives with fluid resistance at its surface of contact with any other member.
With the configurations of conventional technologies, there is a possibility that the following takes place when the area of a surface of contact between a control member and any other member is large: fluid resistance is increased and this degrades response. The viscosity of fuel varies according to temperature. For this reason, the fluid resistance arising from the contact surface portion varies according to temperature. As a result, when the area of a contact surface portion is large, fluctuation in fluid resistance is increased and this can cause injection characteristics to fluctuate.